Our studies of the backbone conformation of the luteinizing hormone releasing factor (LRF) have utilized the two approaches of charge transfer labelling and, more recently, selective replacement of residues by 15N-labelled amino acids. Our research will continue to be directed towards a clearer understanding of the role of conformation in the biological activity of this hormone. New cyclic and linear analogs will be synthesized for study by charge transfer techniques and we will also continue and expand our studies by 15N nmr spectroscopy. We are currently initiating conformational studies of another peptide hormone, somatostatin, a tetradecapeptide containing a disulfide bridge in a ring structure. Circular dichroism and infrared techniques will be applied to the conformational study of this hormone. We also hope to apply the expertise gained from charge transfer studies of LRF to the study of the conformation of somatostatin. BIBLIOGRAPHIC REFERENCES: C.G. Willson, C. Gilon, B. Donzel and M. Goodman. Synthesis of Pyroglutamyl-histidyl-thiazolidine-4-carboxamide, A Biologically Active Analog of the Thyrotropin Releasing Factor. Biopolymers, 15, 2317 (1976). C. Sakarellos, B. Donzel and M. Goodman. (4-Amino-D-Phenylalanine 6) Luliberin. A Biologically Active Analog of the Luteinizing Hormone-Releasing Factor Suitable for Affinity Labeling. Biopolymers, 15, 1835 (1976).